The proposed research program is an investigation of the relatonship between form and function in macromolecular assemblies. Using the combined techniques of electron microscopy and X-ray diffraction, we propose to produce images of the multi-enzyme complexes, pyruvate dehydrogenase (PDC) and ketoglutarate dehyydrogenase (KGDC) showing the arrangement of the component enzymes. The studies will use the techniques of image analysis of electron micrograph, and of X-ray scattering from solutions of the complexes. Knowledge of these structures is important to an understanding of the production of energy in the cell. Moreover, these structures exemplify aspects of macromolecular interactions important in organization. In addition, we are using the techniques of image analysis of electron micrographs to investigate the structure of actin-containing structures found in nonmuscle cells.